Comstock and colleagues weren't standing on the sidelines at practices andgames, screening players for concussions.

It's possible that athletic trainers paid more attention to girls' injuriesor that boys were less likely to report symptoms.

"Traditionally, U.S. society has tended to be more protective of femaleathletes," write the researchers. "This may lead coaches, athletictrainers, and parents to treat head injuries in female athletes more seriouslyor to delay their return to play."

Playing hurt or rushing back from injury is a bad call, Comstock's teamnotes.

They urge people to take athletes' head injuries seriously and allowadequate recovery time, regardless of the player's sex.